Comparison of renal ablation with cryotherapy, dry radiofrequency, and saline augmented radiofrequency in a porcine model

Using an abdominal phantom to teach urology residentes ultrasound-guided percutaneous needle placement

INTRODUCTION

To assess the effect of a hands-on ultrasound training session to teach urologic trainees ultrasound-guided percutaneous needle placement.

MATERIALS AND METHODS

University of California, San Francisco (UCSF) urology residentes completed a time trial, placing a needle into a phantom model target under ultrasound guidance. Participants were randomized into three educational exposure groups: Group 1's time trial occurred prior to any teaching intervention, group 2's after experiencing a hands-on training module, and group 3's after exposure to both the training module and one-on-one attending feedback. Needle placement speed and accuracy as well as trainees' perceived confidence in utilizing ultrasound were measured.

RESULTS

The study cohort consisted of 15 resident trainees. Seven were randomized to group 1, three to group 2, and five to group 3. All residents reported minimal prior ultrasound experience. Their confidence in using ultrasound improved significantly after completing the training module with the most significant improvement seen among junior residents. Time to needle placement was fastest after receiving attending feedback (46.6sec in group 3 vs. 82.7sec in groups 1 and 2, p<0.01). Accuracy also improved with attending feedback, though the number of repositioning attempts did not differ significantly between groups.

CONCLUSIONS

A hands-on training module and use of an abdominal phantom trainer increased resident confidence and skill in their use of ultrasound to guide percutaneous needle positioning. Attending feedback is critical for improving accuracy in needle guidance toward a target. Ultrasound-guided needle positioning is a teachable skill and can be applicable to multiple urologic procedures.

"Edgeboost": A Novel Technique to Extend the Ablation Zone Lateral to a Two-Probe Bipolar Radiofrequency Device

BACKGROUND

The dual-electrode bipolar-RFA (B-RFA) is increasingly used to ablate large liver tumours (3-7 cm). However, the challenging aspect of B-RFA is the placement of the two electrodes around the tumour. Realignment often requires the electrodes to be extracted and reinserted.

AIM

The aim of this study is to examine "Edgeboost", a novel technique to increase the lateral ablation dimension without requiring any realignment of the electrodes.

METHODS AND MATERIALS

An egg-white model and an ex vivo calf liver model were used compare the standard bipolar mode ablation to Edgeboost-1 (reaching full impedance in bipolar mode initially, then cycling in unipolar mode between left and right probes) and Edgeboost-2 (similar to Edgeboost-1 but not reaching full impedance initially in bipolar mode in order to minimize charring and, thus, to increase total ablation time).

RESULTS

A significantly larger outer lateral ablation dimension to the probe was achieved with Edgeboost-1 compared to the standard method in the liver model (1.14 cm, SD: 0.16 vs. 0.44 cm, SD: 0.24, p = 0.04). Edgeboost-2 achieved the largest outer lateral ablation dimension of 1.75 cm (SD: 0.35). A similar association was seen in the egg model. Edgeboost-2 almost doubled the mass ablated with standard bipolar alone (mass ratio: 1:1.94 in egg white and 1:1.84 in liver).

CONCLUSION

This study demonstrates that the novel "Edgeboost" technique can increase the outer lateral ablation dimension without requiring the two inserted electrodes to be reinserted. This would be beneficial for interventionists who use the dual B-RFA.

Determination of the nonlethal margin inside the visible "ice-ball" during percutaneous cryoablation of renal tissue

OBJECTIVE

The study was designed to determine the distance between the visible "ice-ball" and the lethal temperature isotherm for normal renal tissue during cryoablation.

METHODS

The Animal Care Committee approved the study. Nine adult swine were used: three to determine the optimum tissue stain and six to test the hypotheses. They were anesthetized and the left renal artery was catheterized under fluoroscopy. Under MR guidance, the kidney was ablated and (at end of a complete ablation) the nonfrozen renal tissue (surrounding the "ice-ball") was stained via renal artery catheter. Kidneys were explanted and sent for slide preparation and examination. From each slide, we measured the maximum, minimum, and an in-between distance from the stained to the lethal tissue boundaries (margin). We examined each slide for evidence of "heat pump" effect.

RESULTS

A total of 126 measurements of the margin (visible "ice-ball"-lethal margin) were made. These measurements were obtained from 29 slides prepared from the 6 test animals. Mean width was 0.75 ± 0.44 mm (maximum 1.15 ± 0.51 mm). It was found to increase adjacent to large blood vessels. No "heat pump" effect was noted within the lethal zone. Data are limited to normal swine renal tissue.

CONCLUSIONS

Considering the effects of the "heat pump" phenomenon for normal renal tissue, the margin was measured to be 1.15 ± 0.51 mm. To approximate the efficacy of the "gold standard" (partial nephrectomy, ~98 %), a minimum margin of 3 mm is recommended (3 × SD). Given these assumptions and extrapolating for renal cancer, which reportedly is more cryoresistant with a lethal temperature of -40 °C, the recommended margin is 6 mm.

Repeat partial nephrectomy on the solitary kidney: surgical, functional and oncological outcomes

PURPOSE

We examined outcomes in patients with recurrent or de novo renal lesions treated with repeat partial nephrectomy on a solitary kidney.

MATERIALS AND METHODS

We reviewed the records of patients who underwent nephron sparing surgery at the National Cancer Institute from 1989 to 2008. Patients were included in analysis if they underwent repeat partial nephrectomy on a solitary kidney. Perioperative, functional and oncological outcomes were assessed. Functional outcomes were evaluated using the Modification of Diet in Renal Disease equation for the estimated glomerular filtration rate. Oncological efficacy was examined by the need for subsequent repeat renal surgery and the development of metastatic disease.

RESULTS

A total of 25 patients were included in the analysis. A median of 4 tumors were resected. Median estimated blood loss was 2,400 ml and median operative time was 8.5 hours. Perioperative complications occurred in 52% of patients, including 1 death and the loss of 3 renal units. There was a decrease in the estimated glomerular filtration rate at followup visit 1 within 3 months after surgery but at 1-year followup the difference was not significant (p <0.01 and 0.12, respectively). Surgical intervention was recommended in 8 patients (38%) for recurrent or de novo tumors at a median of 36 months. The average metastasis-free survival rate in the cohort was 95% at 57 months (median 50, range 3 to 196).

CONCLUSIONS

Repeat partial nephrectomy in patients with solitary kidney is a high risk alternative. The complication rate is high and there is a modest decrease in renal function but most patients remain free of dialysis with acceptable oncological outcomes at intermediate followup.

Hand-assisted laparoscopic partial nephrectomy: a controlled study of bipolar inline radiofrequency ablation device in Swine

BACKGROUND

Bipolar inline radiofrequency ablation (ILRFA) is an effective way to control bleeding during parenchymal organ transection. This was investigated in a study of laparoscopic hand-assisted partial nephrectomy in swine.

METHODS

Nine Landrace pigs were divided between 2 groups; diathermy was employed in the control group for parenchymal transaction and ILRFA was applied in the experimental group through a hand-port and deployed into the resection plane. After complete coagulation, resection was performed using scissors.

RESULTS

The mean intraoperative blood loss was 32 +/- 15 mL in the ILRFA group and 187 +/- 69 mL in the control group: a 82.9% reduction ( P = .015). The mean blood loss per resection area was 2.53 +/- 0.92 mL/cm(2) in the ILRFA group compared with 17.31 +/- 9.05 mL/cm( 2) in controls; the reduction was 85.4% (P = .005).

CONCLUSIONS

ILRFA is effective in achieving reducing blood loss and provides a drier operative field for precise dissection.

Cryoablation for small renal masses

Advances in imaging techniques (CT and MRI) and widespread use of imaging especially ultrasound scanning have resulted in a dramatic increase in the detection of small renal masses. While open partial nephrectomy is still the reference standard for the management of these small renal masses, its associated morbidity has encouraged clinicians to exploit the advancements in minimally invasive ablative techniques. The last decade has seen the rapid development of laparoscopic partial nephrectomy and novel ablative techniques such as, radiofrequency ablation (RFA), high-intensity focused ultrasound (HIFU), and cryoablation (CA). In particular, CA for small renal masses has gained popularity as it combines nephron-sparing surgery with a minimally invasive approach. Studies with up to 5-year followup have shown an overall and cancer-specific 5-year survival of 82% and 100%, respectively. This manuscript will focus on the principles and clinical applications of cryoablation of small renal masses, with detailed review of relevant literature.

Renal function outcomes in patients treated for renal masses smaller than 4 cm by ablative and extirpative techniques

PURPOSE

We examined the effect of radical nephrectomy, partial nephrectomy and radio frequency ablation on renal function in patients with stage T1a renal masses.

MATERIALS AND METHODS

A total of 242 consecutive patients from July 1995 to March 2005 undergoing primary treatment for unilateral renal masses smaller than 4 cm and a normal contralateral kidney were identified. Renal function was calculated using the modified Modification of Diet in Renal Disease equation. The rate of decrease in the glomerular filtration rate below 60 ml per minute 1.73 m2 was compared among the 3 treatment modalities.

RESULTS

A total of 86, 85 and 71 patients were treated with radio frequency ablation, partial nephrectomy and radical nephrectomy, respectively. Preoperatively stage 3 chronic kidney disease (glomerular filtration rate less than 60 ml per minute per 1.73 m2) was identified in 65 patients (26.7%), including 26.7%, 27.1% and 26.8% who underwent radio frequency ablation, partial nephrectomy and radical nephrectomy, respectively. Following intervention the 3-year freedom from a glomerular filtration rate decrease of below 60 ml per minute per 1.73 m2 for radio frequency ablation, partial nephrectomy and radical nephrectomy was 95.2%, 70.7% and 39.9%, respectively (p <0.001). Multivariate analysis showed that radical nephrectomy was an independent risk factor vs radio frequency ablation and partial nephrectomy for stage 3 chronic kidney disease (HR 34.3, 95% CI 4.28-275 and 10.9, 95% CI 1.36-88.7, respectively).

CONCLUSIONS

Decreased renal function is prevalent in patients with small unilateral renal tumors even with a normal contralateral kidney. Ablative or extirpative nephron sparing techniques are effective for preserving renal function in these patients.

Effect of Freeze Time during Renal Cryoablation: A Swine Model

BACKGROUND AND PURPOSE

Cryotherapy provides a minimally invasive treatment for small renal tumors via an open, percutaneous, or laparoscopic approach. We sought to determine the most appropriate duration of freezing and the number of probes necessary to produce cell death without concomitant morbidity.

MATERIALS AND METHODS

Nine domestic female pigs were divided into three groups of three animals each. Each group underwent a single freeze cycle with a commercially available cryotherapy device with 3.4-mm probes: group 1 for 5 minutes, group 2 for 10 minutes, and group 3 for 15 minutes. The right kidney was treated with a single probe, the left with a double probe. Animals were permitted to survive for an average of 4.8 days (range 4-7 days), after which the kidneys were harvested. A single pathologist examined the kidneys for gross and histologic changes. Evidence of complications (fistula, bleeding, bowel injury) was documented at the time of necropsy.

RESULTS

For group 1, the temperature obtained with a single probe 5, 10, 15, and 20 mm from the probe was -57 degrees C, 3 degrees C, 25 degrees C, and 33 degrees C, respectively; for group 2 -85 degrees C, -37 degrees C, -2 degrees C, and 25 degrees C; and for group 3 -10 degrees C, -45 degrees C, -20 degrees C, and 6 degrees C. For group 1, the temperature obtained with a double probe at 5, 10, 15, and 20 mm from each probe was -65 degrees C, 0 degrees C, 20 degrees C, and 30 degrees C, respectively; for group 2 -72 degrees C, -25 degrees C, 5 degrees C, 25 degrees C; and for Group 3 -82 degrees C, -30 degrees C, -12 degrees C, 13 degrees C. Complete necrosis was seen 5 mm from the cryoprobe within each group, but only in groups 2 and 3 did necrosis extend 10 mm or beyond the probes when utilizing either single or double probes. The maximum diameter of consistent necrosis was 35 to 40 mm in the animals in group 3 treated with a double probe. Bleeding and renal fracture were the two most common complications.

CONCLUSIONS

A 5-minute freeze appears to be inadequate to cause tissue necrosis and is associated with excessive bleeding at the time of the procedure, whereas the 15-minute freeze produces consistent necrosis but is associated with renal fracture. In this animal model, the 10-minute freeze with the single or double probe configuration appears optimal to produce necrosis without complications.

Laparoscopic Radiofrequency Renal Ablation in Patients with Simultaneous Visceral Tumors: Long-Term Follow-Up

PURPOSE

To report our experience with in situ laparoscopic radiofrequency ablation (RFA) of renal tumors.

PATIENTS AND METHODS

From September 2000 to May 2002, two men, 81 and 71 years old, and one woman, 75 years old, were referred to our department for right renal clear-cell carcinoma <3.5-cm diameter. The 71- year-old patient had only one kidney. Because of the tumor location, the percutaneous route was not considered the approach of choice. Moreover, a simultaneous large right adrenal incidentaloma (myelolipoma) and a right colon cancer were known to be present in the second and third patient, respectively. The aforementioned findings suggested the laparoscopic route as a preferable technique to treat both the renal and the other morbidities.

RESULTS

Under laparoscopic ultrasonography control of tine placement, a 20-minute thermoablation cycle at 100 degrees C mean temperature was performed. Including right colectomy and right adrenalectomy, the operative time was 120, 200, and 275 minutes, with postoperative hospital stays of 3, 4, and 6 days for the three patients, respectively. Abdominal CT scans after 1 and 4 weeks and then every 6 months confirmed complete treatment of the lesion at 44 months' average follow-up (range 36-56 months).

CONCLUSION

When percutaneous access is not feasible or the patient should undergo another laparoscopic procedure simultaneously, laparoscopic RFA of renal tumors is feasible and effective, as shown by long-term follow-up.

Radiofrequency Renal Ablation: In Vivo Comparison of Internally Cooled, Multitined Expandable and Internally Cooled Perfusion Electrodes

PURPOSE

To evaluate the in vivo efficiency of radiofrequency ablation using an internally cooled-perfusion (ICP) electrode for inducing coagulation necrosis compared with those of RFA using internally cooled or multitined expandable electrodes in porcine kidneys.

MATERIALS AND METHODS

Using a 200 W generator and internally cooled and ICP electrodes or a 150 W generator and a multitined expandable electrode, a total of 15 radiofrequency ablations were performed in the kidneys of nine pigs. After placement of an electrode in the lower pole of a kidney, one ablation zone was created using one of three different regimens: group A, radiofrequency ablation using an internally cooled electrode; group B, radiofrequency ablation using an ICP electrode with 14.6% NaCl solution instillation at 1 mL/minute; group C, radiofrequency ablation using a multitined expandable electrode. Three days after the procedures, contrast-enhanced CT scans were obtained to evaluate ablation region volumes, and kidneys were harvested for gross measurements. The three groups were compared with respect to technical parameters such as changes in impedance and current during radiofrequency ablation. The dimensions of thermal ablation zones created in the three groups were compared histologically.

RESULTS

In vivo study showed that ICP electrode allowed a greater energy delivery than internally cooled or multitined expandable electrode during radiofrequency ablation: 63.3 +/- 8.8 kJ in group A; 101 +/- 3.3 kJ in group B; and 61.8 +/- 12.5 kJ (P < .05). In vivo studies showed radiofrequency ablation using ICP electrode achieved larger mean coagulation volumes than radiofrequency ablation using the other electrodes: 12.0 +/- 3.9 cm(3) in group A; 30.5 +/- 7.6 cm(3) in group B; and 11.6 +/- 6.7 cm(3) in group C (P < .05). In addition, group B had a larger mean short-axis diameter of radiofrequency-induced coagulation necrosis than groups A or C: 2.6 +/- 0.5 cm in group A; 3.6 +/- 0.4 cm in group B; and 2.4 +/- 0.7 cm in group C (difference between groups B and C: P < .05).

CONCLUSIONS

Radiofrequency ablation using an ICP electrode showed better performance at creating coagulation necrosis than radiofrequency ablation using internally cooled or multitined expandable electrodes in this porcine renal model.

Bipolar and Multipolar Radio Frequency Ablation With Resistance Controlled Power Output: Standardized Ex Vivo Kidney Tissue Evaluation

PURPOSE

We investigated a newly developed bipolar and multipolar RF ablation system with an internally cooled electrode and resistance controlled power output in a standardized model of perfused ex vivo kidney tissue.

MATERIALS AND METHODS

RF energy was applied at different power levels (20, 30 and 60 W) for 1, 3, 5 and 9 minutes. Each treatment parameter was repeated 5 times. For the 20/30 W levels a bipolar electrode with an active conducting part of 20/30 mm was selected. At 60 W 2 bipolar electrodes with an active conducting part (30 mm each) were connected. Lesion volumes and shapes were calculated by measuring the maximum vertical, long axis and short axis diameters of the macroscopic lesion.

RESULTS

Lesion volume increased significantly with the treatment time and generator power applied (p < 0.0001). Lesion size in multipolar ablated zones was larger than that in bipolar ablated zones. A reliable dose-effect relationship existed between the generator power/applied treatment time and ablated tissue lesion size. All lesions were elliptical.

CONCLUSIONS

Bipolar and multipolar RF ablation with an internally cooled electrode and tissue resistance control represent an interesting advance in RF technology. The development of lesion size and volume is predictable, while a uniform lesion shape can be achieved in perfused ex vivo kidney tissue. Further in vivo trials are required to test whether complete and reliable tumor tissue ablation is possible with this system.

Magnetic Resonance Imaging Findings and Histopathological Observations After Percutaneous Renal Cryoablation in the Rabbit Model

PURPOSE

We investigated sequential changes in MRI and relevant histopathological findings after PRC.

MATERIALS AND METHODS

A total of 15 rabbits were examined with MRI and sacrificed immediately (3), and 7 (4), 45 (4) and 90 (4) days after PRC. MRI studies were reviewed for the signal intensity of cryolesions and correlated with pathological findings. MRI and pathological measurements of cryolesion sizes were compared using the paired t test.

RESULTS

CCN was produced in central areas of cryolesions and associated with hemorrhage, hemolysis, fibrous granulation and fibrosis that was orderly through days 1 to 90. Signal intensity was slightly hyperintense on T1-weighted spin-echo images immediately after PRC, and hyperintense on T1 and T2-weighted fast spin-echo images at 7 days. On T2-weighted fast spin-echo images there was a hypointense zone in peripheral areas between the central area and renal parenchyma at the prior 2 stages, which was consistent with PCN histologically. It was enhanced at 7 days. At 45 and 90 days the signal intensity of cryolesions was isointense or hypointense on the 2 sequences. Parenchymal injury adjacent to cryolesions was histologically recognized and visible as a hyperintense zone in 2 lesions at 45 days. This zone was enhanced in 2 lesions at 45 and 90 days. No statistical significance was apparent between the 2 measurements of cryolesions and CCN sizes (p <0.05).

CONCLUSIONS

The MRI appearance of cryolesions reflects orderly histopathological findings. MRI distinguishes CCN from PCN, reveals injury to the renal parenchyma outside of cryolesions and accurately estimates the size of cryolesions and CCN.

Minimally Invasive Treatment of Renal Cell Carcinoma: Comparison of 4 Different Monopolar Radiofrequency Devices

OBJECTIVES

Radiofrequency Ablation is an investigational treatment option for RCC. The aim of our study was to test the ablation algorithms of four different RF systems in a standardized ex vivo perfused porcine kidney model.

MATERIALS AND METHODS

A multiline monopolar dry electrode (impedance-based system), a multiline monopolar dry electrode (temperature-based system), a single monopolar wet electrode (impedance-based system) and a single monopolar dry, internally-cooled electrode (impedance-based system) were selected. RF energy was applied at different treatment parameters (power with and without control, tissue temperature, saline enhancement) for 1, 3, 5 and 9 minutes in healthy perfused ex vivo porcine tissue. Each treatment parameter was repeated 5 times. Maximum vertical, long-axis and short-axis diameters of the macroscopic lesion were measured and lesion volumes/ shapes were calculated.

RESULTS

Lesion volumes increased significantly with the pre-selected tissue temperature and saline enhancement. Saline enhancement created larger, but irregular shaped lesions. The impedance-based system created lesion volumes that were predictable by treatment time and generator power. Lesions were unpredictable when uncontrolled generator power was applied. The created lesion shape was dependent on the selected electrode configuration.

CONCLUSIONS

The currently available monopolar RFA systems offer different specific technical features to control tissue ablation. Detailed knowledge of the specific characteristics of each RF system is necessary to provide a higher chance of successful clinical outcome by complete and reliable ablation.

RENAL CRYOABLATION AND RADIO FREQUENCY ABLATION: AN EVALUATION OF WORST CASE SCENARIOS IN A PORCINE MODEL

PURPOSE

Although ablative technologies, including radio frequency (RF) ablation (RFA) and cryoablation (CA), are being used to treat renal masses, complications associated with injury to vital renal structures are not well understood. We investigated these worst case scenarios by deliberately targeting vital renal structures with CA or RFA in a porcine model.

MATERIALS AND METHODS

Following surgical exposure of the right kidney in female pigs a cryoneedle or an RF probe was deliberately placed under visual and ultrasound guidance in the renal pelvis (CA in 5 pigs and RFA in 7), major calix (CA and RFA in 5 each) or subsegmental renal vessels (CA in 5 pigs and RFA in 7). Cryo-energy or RF energy was then applied to create a 3 cm lesion. After 10 days the kidneys underwent gross and histological examination for urine and blood extravasation, cell death and injury. Ex vivo retrograde pyelography was performed to evaluate for urinary fistulas.

RESULTS

All pigs tolerated the treatment and no procedure related deaths occurred. No significant bleeding was noted. RFA and CA created reproducible lesions and areas of cell death and necrosis. Despite significant intentional injury to the collecting system no urinary fistulas were demonstrated in CA specimens (0 of 15). In contrast, damage to the renal pelvis (4 of 7) by dry (3 of 4) or wet (1 of 3) RFA was associated with a high likelihood of urinary extravasation.

CONCLUSIONS

This short-term study demonstrates that CA is safe, effective and not associated with urinary extravasation. In contrast, RFA to the renal pelvis is associated with urinary extravasation. Further studies are needed to support these findings.

Concepts, Considerations, and Concerns on the Cutting Edge of Radiofrequency Ablation

Radiofrequency (RF) ablation is rapidly expanding from a tool to treat isolated hepatic malignancy to a therapy for patients with renal, adrenal, skeletal, breast, lung, and other soft-tissue neoplasms. The purpose of this article is to review the status of RF ablation outside the liver and lung and compare outcomes with current clinical standards when appropriate. The author also reviews how differences in local tissue environments play a role in creation of a thermal lesion and achievement of subsequent clinical success.

Percutaneous radiofrequency ablation of renal cell carcinoma

BACKGROUND

Preliminary data regarding the use of percutaneous radiofrequency ablation (RFA) for the treatment of renal cell carcinoma (RCC) are encouraging, and show the technique to be associated with minimal morbidity. Thus, the current study was designed to evaluate the clinical applications, treatment efficacy, and complications of percutaneous RFA in RCC.

METHODS

From February 2003 to February 2004, 12 consecutive patients with histopathologically proven RCC underwent imaging-guided percutaneous RFA. The mean age of the patients (8 men and 4 women) was 76 years (range, 56-87 years), and mean tumor diameter was 3.7 cm (range, 2.2-8.0 cm). The efficacy of RFA was evaluated with contrast-enhanced, dynamic computed tomography (CT) performed 1 month after treatment, and then every 3 months. A Radionics device with an internally cooled electrode was used in 7 patients, and a radiofrequency interstitial tissue ablation (RITA) device with an expandable needle electrode was used in 5. Complete necrosis was defined as a lack of contrast enhancement in the treated region on follow-up CT studies.

RESULTS

Overall, 16 sessions of RFA were performed for 12 solitary renal tumors in 12 patients: 8 patients underwent a single RFA session, whereas 4 had 2 sessions. Dynamic CT after RFA showed complete necrosis in 9 of 12 tumors. In 3 patients with tumors of 4.5-8.0 cm in diameter, enhancement of residual tissue was observed after RFA treatment, thus indicating residual tumor. Complete tumor necrosis was seen in all 5 tumors (100%) of diameter < or = 3.0 cm; 3 of 4 tumors (75%) of diameter 3.1-5.0 cm; and 1 of 3 tumors (33%) of diameter > 5.0 cm. A big subcapsular hematoma, which was found in 1 patient after RFA, resolved completely within 10 months without treatment; no serious complications occurred in the other 11 patients.

CONCLUSION

Percutaneous RFA is effective in the treatment of RCC. It is most successful for tumors not larger than 3 cm in diameter, and has a satisfactory success rate in tumors of 3-5 cm in diameter. The rate of serious complications of RFA is low. Further studies are necessary to determine the long-term efficacy of RFA in RCC.

Comparison of renal ablation with monopolar radiofrequency and hypertonic-saline-augmented bipolar radiofrequency: in vitro and in vivo experimental studies

OBJECTIVE

We sought to determine whether hypertonic-saline (HS)-augmented bipolar radiofrequency ablation has advantages over monopolar radiofrequency ablation for creating larger areas of coagulation necrosis in the kidney.

MATERIALS AND METHODS

Using a 200-W generator and bipolar perfused-cooled electrodes or a monopolar cooled-tip electrode, we performed 14 radiofrequency ablations in explanted bovine kidneys. Radiofrequency was applied in standard monopolar (n = 7) or bipolar (n = 7) modes at 100 W for 10 min. In the bipolar mode, the perfused-cooled electrodes were placed at interelectrode distances of 3 cm, and a 6% sodium chloride solution was instilled into tissue at a rate of 2 mL/min through the electrodes. For in vivo experiments, either monopolar (n = 7) or HS-augmented bipolar (n = 7) radiofrequency ablation was performed in the lower pole of canine kidneys. Three days after the procedure, contrast-enhanced CT scans were obtained to evaluate the volumes of the ablation regions, and the kidneys were harvested for gross measurements. Technical parameters such as changes in impedance and current during radiofrequency ablation and dimensions of the thermal ablation zones were compared between the two groups.

RESULTS

In ex vivo and in vivo experiments, the frequency of the pulsed radiofrequency application caused by rises in impedance was higher in the monopolar mode than in the bipolar mode during the application of radiofrequency energy. The in vivo study showed that the bipolar radiofrequency ablation allowed larger mean current flows than the monopolar radiofrequency ablation (i.e., mean +/- SD, 1,654 +/- 144 mA vs 967 +/- 597 mA) (p < 0.05). Ex vivo studies revealed that the volumes of bipolar radiofrequency-induced ablation regions were substantially larger than those of monopolar radiofrequency-induced ablation regions (26.1 +/- 10.5 cm(3) vs 10.2 +/- 4.2 cm(3)). In vivo studies showed bipolar radiofrequency ablation achieved larger coagulation necrosis than monopolar radiofrequency (3.2 +/- 0.3 cm vs 2.4 +/-0.4 cm) (p < 0.05). This was confirmed by the measured volume of nonenhancing area on contrast-enhanced CT (20.4 +/- 6.4 cm(3) vs 13.5 +/- 6.0 cm(3)).

CONCLUSION

HS-augmented bipolar radiofrequency ablation using perfused-cooled electrodes shows better performance in creating coagulation necrosis than monopolar radiofrequency ablation in the kidney of an animal model.

Radiofrequency tissue ablation in an experimental model of grade IV renal trauma: a preliminary report

BACKGROUND

The kidney is one of the most frequently injured intraabdominal organs. In this study, we investigated the efficacy and safety of radiofrequency ablation (RFA) as a kidney-preserving hemostatic technique for grade IV renal trauma.

METHODS

A grade IV injury was induced in the right kidney of 12 Landrace pigs. Then RFA was applied around the injury in 10 animals until hemostasis was achieved; two animals were not treated (control group). The treated animals were killed humanely on days 0, 3, 7, 14 and 21 and examined. The kidneys were subjected to histologic and radiologic examination.

RESULTS

The two untreated animals died from hypovolemic shock. Hemostasis was achieved in all treated animals. We had no operative deaths and no morbidity. No blood, pus, urine, or other fluid was found at the time of death. In one animal, a fistulous lesion leading to the collecting system was identified, but no urine leakage was observed. At histology, the ablated areas were found to consist of three zones: an inner necrotic one, a zone of neutrophils digesting necrotic tissue, and an outer zone with possibly reversible damage.

CONCLUSIONS

Radiofrequency ablation is an efficient and safe hemostatic method for grade IV renal trauma. Further study is needed to investigate the possible application of this method to humans and its percutaneous or laparoscopic use.

Volumetric thermal devascularization of large meningiomas

Object. Controlling hemorrhage is crucial in the safe and efficient removal of large meningiomas. Intravascular embolization is not always a satisfactory means of accomplishing this goal because of the procedure's hemostatic effect and risk of complications. The authors in this study used a volumetric thermal ablation technique incorporating radiofrequency energy, image guidance, and local temperature control to devascularize tumor tissue.

Methods. Five patients with large meningiomas were treated. The target and orientation of the radiofrequency thermal ablation (RFTA) were simulated preoperatively to maximize devascularization of the lesion without thermal injury to adjacent critical structures. Image fusion, three-dimensional reconstruction, and image-guided methods provided for optimized trajectories and targets for insertion of the RFTA needle. During ablation, local temperatures of the tissue being cauterized were monitored continuously to limit the ablated lesion to within the target volume.

The effects of devascularization and the softening of the tumor parenchyma facilitated lesion removal. The intracranial ablated meningioma changed into necrotic tissue and shrank within a few months. Histopathological examination of the ablated lesion revealed sharply demarcated coagulation necrosis.

Conclusions. Volumetric thermal devascularization can be applied safely in the treatment of large meningiomas to facilitate surgical manipulation of the lesion as well as to reduce its size palliatively. The procedure's usefulness should be studied further in a larger number of cases with different tumor characteristics.

Comparison of Radiofrequency Ablation, Cryoablation, and Nephrectomy in Treating Implanted VX-2 Carcinoma in Rabbit Kidneys

PURPOSE

To compare the efficacy of radiofrequency (RF) ablation, cryoablation, and radical nephrectomy in the treatment of implanted VX-2 carcinoma in rabbit kidneys.

MATERIALS AND METHODS

Sixty-eight New Zealand White rabbits were implanted with 1-mm3 segments of VX-2 carcinoma in the left kidney. Seven days after implantation, the tumors were treated with one of the following: (1) RF ablation using a 12-gauge electrode (RITA Medical Systems, Mountain View, CA) at 90 degrees C for 8 minutes with a 5-mm tumor margin target temperature of 60 degrees C (N = 20); (2) cryoablation using a 15 minute double-freeze technique with 2.4-mm cryoprobes and the Cryocare system (Endocare Inc., Irvine, CA) with a 5-mm tumor margin target temperature of -20 degrees C (N = 20); (3) open radical nephrectomy (N = 20); or (4) no treatment (controls; N = 8). Rabbits were allowed to survive for a total of 22 days and sacrificed; and the kidneys, lungs, liver, spleen, urinary bladder, and ureter were removed and examined grossly and histologically for tumor.

RESULTS

Findings in animals sacrificed at 15 days post-treatment showed significant differences between all treatment groups and untreated controls (P < 0.002) Using a 3 x 2 chi-square comparison, no differences in disease-free survival were observed between the RF ablation group, the cryoablation group, and the open nephrectomy group (P = 0.72)

CONCLUSION

Radiofrequency ablation, cryoablation, and radical nephrectomy were all efficacious in the treatment of implanted VX-2 renal tumors compared with untreated controls (P = 0.002). No statistically significant difference was found between any of the three treatments.

Primary care update on kidney and bladder cancer: a urologic perspective

The past decade has witnessed many substantive changes in the approach to the diagnosis and treatment of both kidney and bladder cancer. In part, this is based on changes in the understanding of their carcinogenesis and pathogenesis, an appreciation of new concepts in their classification, and the incorporation of new technologies that have emerged. This article reviews advances and updates changes that have been made in the understanding of and approaches to these malignancies from the perspective of their urologic assessment and management while in the context of primary care issues.

Emerging Nephron Sparing Treatments for Kidney Tumors: A Continuum of Modalities From Energy Ablation to Laparoscopic Partial Nephrectomy

PURPOSE

The current global medical trend toward minimally invasive treatment for various tumors has generated special interest in several minimally invasive options in the management of kidney tumors. We discuss the role of nephron sparing surgery by less invasive options than the time-honored partial nephrectomy, and the current multitude of energy based tumor ablative methods.

MATERIALS AND METHODS

We searched the English literature following the introduction of nephron sparing surgery, with special attention to various emerging minimally invasive surgical and ablative alternatives.

RESULTS

Laparoscopic partial nephrectomy can be performed safely following the surgical oncology principles established by open partial nephrectomy. Initial results from the various energy based modalities, most notably cryoablation, indicate that high local control rates can be achieved. However, caution is advised since viable tissue has been observed after minimally invasive ablative therapies. Available data, while promising, are still lacking for long-term followup.

CONCLUSIONS

Compared to open partial nephrectomy the laparoscopic approach offers similar cancer-free survival rates. However, the procedure requires highly skilled surgeons. Of the energy based ablative treatments cryoablation followed by radio frequency ablation offers the most meaningful results, with promising local control rates indicated in some series. These methods can be performed less invasively than partial nephrectomy and require less surgical expertise. We anticipate that these modalities will be formalized into urological practice and serve as a single continuum of care, customized according to disease and surgical expertise.

Bipolar Radiofrequency Ablation of the Kidney: Comparison with Monopolar Radiofrequency Ablation

PURPOSE

We report initial ex vivo and in vivo studies using bipolar radiofrequency (RF) ablation of porcine kidneys. An internal ground electrode is positioned in the kidney opposite the RF electrode, resulting in ablation of all the intervening renal tissue.

MATERIALS AND METHODS

Ex vivo preparations of 10 porcine kidneys were perfused continuously with Ringer's solution and treated with either standard external grounded RF (N = 3) or bipolar RF ablation with 1 (N = 2), 2 (N = 3), or 3 (N = 2) cm of separation between the ground probe and the RF probe using a Model 30 RITA generator (RITA, Mountain View, CA). Target temperatures were 90 degrees C for 8 minutes. Gross and histologic assessments were made acutely. Four domestic pigs were treated with monopolar RF ablation of the lower pole of one kidney and bipolar RF with a 12-mm separation between the probes of the contralateral lower pole. Animals were harvested 48 hours later to maximize tissue damage for gross measurements and histologic evaluation.

RESULTS

Ex vivo studies revealed grossly monopolar lesions 1.5 cm in maximum diameter and 1.75 cm(3) in volume. In comparison, bipolar lesions were 2.8 cm in maximum diameter and 10.3 cm(3) in volume using 3 cm of electrode separation. There was histologic evidence of cell death in all specimens. In vivo studies showed two distinct gross lesions with RF: one blanched and one hemorrhagic. Using bipolar RF, larger blanched lesions were achievable than with monopolar RF (2.80 cm(3) v 1.63 cm(3)). Overall, the combinations of blanched and hemorrhagic lesions were similar with monopolar and bipolar RF (5.01 v 5.31 cm(3)). Histologic evaluation verified cell death in the blanched lesions and rare areas of normal tissue in the hemorrhagic lesions.

CONCLUSIONS

As shown by ex vivo data, bipolar RF can create larger lesions than does monopolar RF. In vivo, at 48 hours, both blanched and hemorrhagic gross lesions were seen using RF. In this model, blanched lesions predominated when performing bipolar RF.

Comparative analysis of laparoscopic versus open partial nephrectomy for renal tumors in 200 patients

PURPOSE

Laparoscopic partial nephrectomy is an emerging minimally invasive, nephron sparing approach for renal cell carcinoma. We compared perioperative outcomes after laparoscopic and open nephron sparing surgery (NSS) for patients with a solitary renal tumor of 7 cm or less at a single institution.

MATERIALS AND METHODS

Since September 1999, 100 consecutive patients have undergone laparoscopic partial nephrectomy for a sporadic single renal tumor of 7 cm or less at our institution. A contemporary cohort of 100 consecutive patients with similar inclusion criteria have undergone open NSS since April 1998. Since our laparoscopic technique was based on our established open surgical principles, the 2 approaches were similar, including transient renal vascular control, sharp tumor excision in a bloodless field, pelvicaliceal repair when necessary, suture ligation of transected intrarenal blood vessels and suture repair of the renal parenchymal defect over a bolster. Demographic, intraoperative, postoperative and short-term followup data were retrospectively compared between the 2 groups.

RESULTS

Median tumor size was 2.8 cm in the laparoscopic group and 3.3 cm in the open group (p = 0.005). There were significantly more tumors greater than 4 cm in the open group (p <0.001). There were more patients with a solitary kidney in the open surgical group (p = 0.002). More patients in the open group underwent NSS for a malignant tumor (p = 002). Comparing the laparoscopic versus open groups, median surgical time was 3 vs 3.9 hours (p <0.001), blood loss was 125 vs 250 ml (p <0.001) and mean warm ischemia time was 27.8 vs 17.5 minutes (p <0.001), respectively. In the laparoscopic and open groups median analgesic requirement was 20.2 vs 252.5 mg morphine sulfate equivalents (p <0.001), hospital stay was 2 vs 5 days (p <0.001) and average convalescence was 4 vs 6 weeks (p <0.001). Median preoperative serum creatinine (1.0 vs 1.0 mg/dl, p = 0.52) and postoperative serum creatinine (1.1 vs 1.2 mg/dl, p = 0.65) were similar in the 2 groups. No kidney was lost due to warm ischemic injury. Three patients in the laparoscopic group had a positive surgical margin compared to none in the open groups (3% vs 0%, p = 0.1). Laparoscopic NSS was associated with a higher rate of major intraoperative complications (5% vs 0%, p = 0.02). There were no significant differences in overall postoperative complications, although renal/urological complications were more common in the laparoscopic group (11% vs 2%, p = 0.01).

CONCLUSIONS

Open surgical partial nephrectomy remains the established standard for nephron sparing treatment of renal tumors. When applied to small renal tumors, the laparoscopic approach is associated with longer warm renal ischemia time, more major intraoperative complications and more postoperative urological complications. Our data also suggest that more deliberate efforts to achieve a wider surgical margin are necessary with the laparoscopic approach. Nevertheless, our data suggest that laparoscopic NSS is emerging as an effective, minimally invasive therapeutic approach with respect to renal functional outcome with the additional advantages of decreased postoperative narcotic use, earlier hospital discharge and a more rapid convalescence. Continued efforts are required to develop laparoscopic renal hypothermia techniques and facilitate intrarenal suturing, while minimizing warm ischemia time.

Imaging-guided percutaneous radiofrequency ablation of solid renal masses: techniques and outcomes of 38 treatment sessions in 32 consecutive patients

OBJECTIVE

The purpose of this study was to describe the treatment techniques and results of 38 consecutive imaging-guided percutaneous radiofrequency ablations of solid renal masses performed in 32 patients.

MATERIALS AND METHODS

Solid renal masses in 32 patients underwent 38 treatment sessions using imaging-guided percutaneous radiofrequency ablation. During 36 sessions, radiofrequency ablation was performed using CT guidance, and two, using sonographic guidance. The average patient age was 76 years (range, 52-87 years), and the average renal mass size was 2.6 cm (range, 1-5 cm). The average number of radiofrequency treatments per solid mass at each session was 2.4 (range, 1-6 treatments), and the average time per treatment was 9.2 min (range, 3-14 min). A single electrode was used in 12 sessions, and a cluster electrode was used in 26 sessions. The average follow-up time was 9 months (range, 1-36 months).

RESULTS

Twenty-six of 32 patients had successful treatment of the solid renal mass using percutaneous imaging-guided radiofrequency ablation after one treatment session. Successful treatment was defined as lack of enhancement of the treated region on follow-up CT. Six of 32 patients had residual enhancing tissue after the first treatment session and returned for a second session. Five of these six retreatments were successful. Masses requiring a second treatment session were significantly larger than masses treated in a single session (3.5 vs 2.4 cm, respectively; p = 0.0013). Two patients had perinephric hematomas (which did not require transfusion), and one patient developed a 5-mm skin metastasis at the electrode insertion site, which was resected without recurrence.

CONCLUSION

Percutaneous imaging-guided radiofrequency ablation shows promise in the treatment of solid renal malignancies.

Renal cryotherapy: 2003 clinical status

PURPOSE OF REVIEW

Traditionally, curative therapy for most renal cancers involved open radical nephrectomy. However, as increased radiological monitoring has led to more incidentally discovered small renal masses, the optimal treatment has evolved. Nephron-sparing surgery, initially developed for patients with solitary kidneys or compromised renal function, emerged as the treatment of choice for small renal masses. It has been shown that long-term cancer control and renal function after partial nephrectomy equals the results of radical nephrectomy. Cryoablation of small renal masses represents an alternative method for performing nephron-sparing surgery.

RECENT FINDINGS

Cryoablation of renal tumors with ultrasound monitoring may be performed under open exposure, but laparoscopy provides equivalent exposure with less morbidity. Cryotherapy may also be performed percutaneously with magnetic resonance image monitoring. After treatment, patients require diligent radiographic monitoring, more frequently than after surgical extirpation.

SUMMARY

The durability of renal cryotherapy appears promising. More data are required to provide reliable treatment of tumor margins for larger lesions, and further to determine the safety of use near the collecting system and renal hilum. Currently, cryoablation of small renal lesions is minimally invasive, safe, and efficacious for select peripheral lesions in carefully selected patients.

Percutaneous computed tomography-guided radiofrequency ablation of renal masses in high surgical risk patients: preliminary results

This article evaluates the safety and efficacy of percutaneous radiofrequency ablation (RFA) delivered by computed tomography (CT) fluoroscopic guidance for the treatment of small, solitary renal lesions in high risk surgical and anesthetic patients. In total, 29 patients with 35 small (</=4 cm) renal lesions underwent a total of 37 CT fluoroscopically guided RFA treatments using a dry RFA technique. Because of medical comorbidities, 26 patients were considered high surgical risk candidates, and 3 patients had von Hippel-Lindau disease. Procedures were performed percutaneously, under intravenous sedation and on an outpatient basis. Renal lesions were monitored on a 3-month basis using precontrast- and postcontrast-enhanced CT imaging to assess for the presence of growth or residual lesion enhancement. Of 37 RFA treatments, 35 (95%) were successfully performed under intravenous sedation and 32 (86%) treatments were performed on an outpatient basis. Over a mean radiographic follow-up period of 9 months, 33 of 35 (94%) renal lesions have required only a single RFA treatment, and 2 patients required a second, successful retreatment for small regions of residual enhancement on follow-up CT imaging. Of 13 renal lesions with a >/=12-month radiographic follow-up interval, 11 (85%) have demonstrated no residual enhancement or growth after RFA. Percutaneous RFA of small, solitary renal lesions is well tolerated in high surgical risk patients. Although early results are encouraging, longer-term follow-up time is necessary to determine the precise role of RFA in this patient population. high resolution video, medium resolution video, low resolution video

Laparoscopic partial nephrectomy and minimally invasive nephron-sparing surgery

Surgical extirpation remains the most effective therapy for renal cell carcinoma. The surgical management of renal masses has evolved away from radical nephrectomy and now includes nephron-sparing surgery for small tumors. Nephron-sparing surgery has similar cure rates and does not appear to compromise cancer control. As the detection of small renal masses by widespread abdominal imaging continues to increase, so will the demand for minimally invasive nephron-sparing procedures. Despite progress in surgical techniques, laparoscopic partial nephrectomy remains a technically challenging procedure. In this review, we discuss the challenges and recent advances in laparoscopic partial nephrectomy and other minimally invasive approaches to renal masses.

Incomplete renal tumor destruction using radio frequency interstitial ablation

PURPOSE

We evaluate the efficacy of temperature based radio frequency ablation as a potential treatment modality for small (less than 3.5 cm.) renal tumors.

MATERIALS AND METHODS

We treated 15 patients with a total of 20 tumors with radio frequency ablation through an open surgical approach immediately before partial nephrectomy. All tumors were biopsied before radio frequency ablation treatment. Tumors were heated to 90 to 110C for 6 to 16 minutes (mean 9.1). Tumor ablation was monitored by direct vision and ultrasound. Partial nephrectomy was performed in standard fashion. All specimens were stained with hematoxylin and eosin, and 5 specimens were stained for nicotinamide adenine dinucleotide (NADH) diaphorase activity.

RESULTS

Tumors ranged from 1.5 to 3.5 cm. (mean 2.4) in greatest dimension. All 20 specimens had evidence of morphologically unchanged tumor and normal renal parenchyma on standard hematoxylin and eosin staining. Of the 5 specimens 4 stained positively for NADH in areas confirmed to be tumor in hematoxylin and eosin stained neighboring sections. There was 1 intraoperative renal pelvic thermal injury requiring pyeloplasty and 2 postoperative caliceal leaks requiring stent placement.

CONCLUSIONS

In our series radio frequency therapy did not result in total tumor destruction when specimens were examined with hematoxylin and eosin or NADH staining. We believe that radio frequency interstitial tumor ablation of renal cell carcinoma without subsequent tissue resection should continue to be an investigational treatment modality for those who would otherwise undergo partial or radical nephrectomy.